To solve the leakage problem encountered on centrifugal equipment, such as pumps compressors and fans, at the point where the rotating shaft penetrates the stationary casing, components such as packing and mechanical seals are used. However these components fail from time to time resulting in releases of handled fluid to the environment and sometimes damage to the equipment. To avoid this problem permanent magnetic drives that work inside the handled fluid envelope were developed. Also can pumps where the induction motor rotor is inside the handled fluid envelope was developed. These two solutions have the problem that the internal shaft and bearings are in contact with the pumped fluid which also has to serve as the lubricating medium. This creates internal shaft/bearing maintenance problems. Additional drawbacks of the can pump approach are: the effect that motor rotor induced currents can have on the pumped fluid, an the prime mover must be an induction motor.
The development of magnetic bearings used in combination with can pumps has obviated the leakage and internal bearing maintenance problems in centrifugal pumps, however the drawbacks of the effects of motor rotor induced currents and limitation to the use of an induction motor as a prime mover remains.
The magnetic bearings mentioned above, consist of stationary electromagnets that induce magnets on the equipment rotor shaft, and by controlling current to the electromagnet, produce equipment rotor levitation. They are also used with prime movers external to the equipment casing such as large centrifugal pumps, centrifugal compressors and centrifugal fans, mechanical seals are required for these cases.
To eliminate such problems, can pumps were developed. Can pumps have the induction motor rotor inside the handled fluid envelope. Such solutions have the problem that the internal shaft and bearings are in contact with the pumped fluid. Also, the pumped fluid serves as the lubricating medium. This creates internal shaft/bearing maintenance problems. Additional drawbacks of the can pump approach include, without limitation, the effect that motor rotor induced currents can have on the pumped fluid and the prime mover must be an induction motor.
Generally, the development of magnetic bearings used in combination with can pumps has obviated the leakage and internal bearing maintenance problems in centrifugal pumps. However, the drawbacks of the effects of motor-rotor induced currents and the limitation associated with the use of an induction motor as a prime mover remains.
The magnetic bearings, known in the art and discussed above, consist of stationary electromagnets that induce magnets on the equipment rotor shaft. By controlling the current to the electromagnet, levitation of the equipment rotor is possible. Such devices are also used with prime movers external to the equipment casing, such as, for example, large centrifugal pumps, centrifugal compressors and centrifugal fans. In these devices, mechanical seals are required.
Sensing devices are also known. For, example strain gauges are known. Strain gauges have been used to measure stress, pressure and torque. Further, rotating transmission rings and fixed pick-up devices have been used for years for the conveyance of control and power electric currents between fixed and rotating parts in electric generators and motors.
It is, therefore, a feature of the present invention to provide an electromagnetic coupled/levitated drive for rotating equipment.
Another feature of the present invention is to provide, as part of a driven rotor, an active component of the driven equipment such as a pump or compressor impeller.
Another feature of the present invention is to provide an electromagnetic coupled/levitated drive suitable for use with different types of prime movers such as electric motors, combustion engines and gas or steam turbines.
Yet another feature of the invention is to provide, for centrifugal pumps, centrifugal compressors and centrifugal fans, a true sealed unit that makes it impossible the escape of polluting fluids to the environment.
Another feature of the present invention is to provide, for centrifugal pumps, centrifugal compressors and centrifugal fans, the possibility to use different types of prime movers and without inducing currents in the pumped fluid,
Another feature of the present invention is to provide, for centrifugal pumps, centrifugal compressors and centrifugal fans, a levitating rotor which eliminates the possibility of internal bearing failure, diminishes equipment down time and reduces maintenance.
Yet another feature of the invention is to provide, for centrifugal pumps, centrifugal compressors and centrifugal fans, a reduction of equipment vibration.
Still another feature of the present invention is to provide, for a tube pump that practices the present invention.
Yet still another feature of the present invention is to provide, for the tube pump, reduced NPSH requirement.
Another feature of the present invention is to provide, for the tube pump, the ability to handle large pieces of solids with the liquid fluid.
Another feature of the present invention is to provide, for the tube pump, ease of installation on an existing line.
Another feature of the present invention is to provide, for the tube pump, no change in flow direction for single stage applications.
Additional features and advantages of the invention will be set forth in part in the description which follows, and in part will become apparent from the description, or may be learned by practice of the invention. The features and advantages of the invention may be realized by means of the combinations and steps particularly pointed out in the appended claims.